1. Field of the Invention
This invention relates to a labelling machine for the placing of labels onto containers, in particular, to the placing of labels onto containers in such a manner that the label constitutes visible proof that the container has not been opened. One such type of container is a beverage bottle which has a screw-top closure. A labelling machine of this type generally comprises a labelling station with a gripper cylinder for applying labels to separable sections of the containers, and a turntable equipped with an inlet star wheel and an outlet star wheel, each of which has receptacles for moving the containers, into, along and out of the labelling machine.
2. Background Information
For reasons of safety, containers which are filled with food or drink, and in particular beverage bottles which have reclosable tops, such as screw-top or snap-top closures, must meet the requirement of constituting visible proof that the bottle has not been opened after the bottle has been filled with a beverage and sealed. Thus, the consumer can visually determine whether the bottle has been opened after the original closing by the bottler.
For snap-top bottles, this protection is achieved by means of a tear strip, which is glued onto the container below the snap-top, while for screw-top bottles, there is generally a plastic or metal ring on the bottom edge of the screw-top, which ring breaks off from the rest of the top when the bottle is opened. However, this very effective means of protection of the screw-top is more expensive than the protection given by the tear strip used for snap-top bottles. This ring, when made of metal, also has the additional disadvantage that when the bottle is opened, sharp edges may be left on the ring, which sharp edges represent a potential source of injury to the user. Because of the above-mentioned shortcomings for screw-top closures, efforts are currently being directed towards protecting even screw-top closures with a strip label.
On a known labelling machine, an applicator element exists for applying hot adhesive to a reserved area of the label. This reserved area does not receive the wet adhesive that is applied to the remainder of the label. The application element itself, is designed as a roller and is located on the gripper cylinder. Thus, the hot adhesive is applied in a single rolling process to the reverse side of the label being held by the gripper cylinder. The label, to which cold, or wet adhesive, and also hot adhesive have been applied, is then transferred from the gripper cylinder to a container being moved past the gripper cylinder, whereby the label is pressed onto both the closure of the container and also onto the portion of the container directly below the closure. The section of the label that is attached to the closure is preferably the only section that receives the hot adhesive. If necessary, adjustable pressure mechanisms can also be used to assist in the pressing process. This type of labelling for containers, however, has a series of disadvantages, as enumerated below.
1. If there is no label in the gripper cylinder, the pressure pad designed to support the reverse side of the label will receive the application of adhesive from the applicator roller as the roller rolls over the pad. This can lead to disruptions during the rest of the labelling operation, because the subsequent labels will stick to, and often remain stuck to the pressure pad of the gripper cylinder, and therefore will no longer be transferred to the bottles which are being labelled.
2. The hot adhesive applied to the reserved area of the label reduces the rigidity of the label, so that as the label continues its travel to the transfer point on the turntable, it has a tendency to curl. A perfect transfer to the bottle closure is then essentially impossible.
3. When the pre-glued label is pressed against the closure of the bottle, the hot adhesive is generally no longer at a high enough temperature to achieve an optimal adhesion. Temperatures of more than 100.degree. C. are generally required for optimal adhesion between the hot adhesive on the label and the plastic or metal closure, which metal closure is usually coated with plastic or paint.